On Mon, 10 Dec 2012, Raviraj Bhat wrote: > Feature to truncate user sense buffer was added in the following patch: > "http://marc.info/?l=linux-usb&m=123135651222832"; No. There is no such feature. The patch you're referring to added a feature to allow sense buffers larger than 18 bytes. > There is a possibility of user application misinterpreting it as a > driver bug as scsi standard or SAT spec do not mention this behavior. > > I would like to ask the experts about the advantages of this feature > for user level applications? If user buffer is capable of holding > complete buffer as returned by device, why can't we just fill the > complete buffer as it is instead of truncating the buffer length? Because data cannot be transferred directly from the device to the user's buffer. It has to go through a kernel buffer first, and the size of that kernel buffer must be known beforehand. Furthermore, quite a few USB storage devices will crash if asked to send anything other than 18 bytes of sense data. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
